Electrical potentials are generated by ionic current flows within the neurons of the brain. Such current flows can be detected by electroencephalography (EEG). EEG devices record the brain's electrical activity and display it in the form of an electroencephalogram (EEG), which generally depicts waveforms of varying frequency and amplitude as measured in voltage. EEG waveforms are generally classified according to their frequency (standard frequency ranges termed alpha, beta, theta, and delta), amplitude, and shape, as well as by the sites on the scalp at which they are recorded.
An irregular brain wave pattern can be indicative of a particular brain pathology. Distinctive EEG patterns are seen, for example, in acquired brain injury (ABI), accelerated cerebral edema, expanding intracranial masses, and severe cerebral ischemia. Such patterns include encephalographic seizures, markedly slow frequencies, amplitude suppression, “burst suppression,” and periodic epileptiform discharges (PEDS) (Jordan 2004, Khan et al 2005, Schneider 2005). While not specific for particular diagnoses, these patterns provide an early, sensitive and reliable warning of severe or worsening brain damage.
The use of EEG when brain injury is suspected is of particular importance because EEG can detect injuries at an early stage, before they progress to more serious conditions. For example, in moderate to severe traumatic ABI, such as from the blast of an explosion or a concussive impact, or in non-traumatic ABI from a stroke or hemorrhage, death or irreversible brain injury are most closely associated with “secondary progression” events that can be detected with EEG, including brain edema, enlarging hemorrhages, seizures, torn or occluded blood vessels, and brain herniation. In the context of acute traumatic brain injury (ATBI), EEG can provide an early warning of worsening brain damage and provide clues about the underlying disease process.
Conventional continuous EEG (CEEG) methods have changed little in decades, and are both inefficient and labor intensive. EEG is oftentimes not readily available, even in hospitals, and delays of hours may occur before an EEG procedure is performed and the results interpreted. Such delays can result in a patient not receiving appropriate treatment, resulting in preventable and sometimes irreversible harm to the patient. The complexity and time involved in applying electrodes to a patient's scalp using traditional EEG can contribute to such delays, as can the absence of a physician or a technician trained to interpret EEG results in a hospital.
There remains a need, therefore, for real-time, functional brain state assessment technology which can be performed in a variety of settings where it may be needed, for example in sports venues, emergency response situations, and battlefield settings.